The chemicals may disrupt the body’s ability to burn calories and lead to more rapid weight gain following dieting.
Photograph: E Hamilton West for the Guardian

Chemicals used to make non-stick pots and pans, stain-resistant carpets, and food packaging may contribute to high levels of obesity by disrupting the body’s ability to burn calories, scientists say.

Researchers at Harvard University examined the effects of compounds called perfluoroalkyl substances (PFASs), which have already raised concerns among some health experts after animal experiments and other studies linked them to cancer, high cholesterol and immune problems.

In the latest work, Qi Sun, a nutritionist who specialises in the risk factors for diabetes, obesity, and cardiovascular disease, analysed records for 621 overweight and obese people who spent six months dieting. All were part of a clinical trial run in the 2000s to test the effectiveness of different types of diets.

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As expected, those on the trial lost weight – on average 6.4kg over the six months of the diet – and then regained nearly half of that in the following 18 months. But Sun found that those who gained the most weight after dieting had the highest blood levels of PFAS chemicals, with the effects more pronounced in women.

According to a report in the journal Plos Medicine, women in the study with the highest PFAS levels re-gained about 2kg more than those with the lowest PFAS levels. The scientists went on to show that those with high levels of PFAS in their blood also burned calories more slowly than the rest, as measured by their resting metabolic rate.

“These chemicals may lead to more rapid weight gain after dieting,” Sun told the Guardian. “It is very hard to avoid exposure to PFASs, but we should try to. It’s an increasing public health issue.”

Figures compiled by the European Food Safety Authority suggest that exposure to certain types of PFASs in Europe are far below the tolerable daily intake (TDI), the amount of a chemical deemed to be safe to consume over a human lifetime. For one compound, perfluorooctane sulfonate, the typical adult consumed less than 3.5% of the TDI.

Alan Boobis, professor of toxicology at Imperial College, London, said that while the findings were intriguing, it was impossible to know whether perfluoroalkyl compounds were responsible for the weight gain seen in the study. “As the authors point out, there is the potential that at least some of the findings are due to chance.

“The findings can serve as a good basis for further, more focused investigations into a possible link between exposure to PFASs and weight management,” he said.